Internal-combustion engine



Filed Nov. l, 1945 2 Sheets-Sheet 1 May 27, l94?. A. GUARALDI INTERNAL COMBUSTION ENGINE Filed Nov. 1, 1945 2 Sheets-Sheet? Z INIV/ENTOR:

Patented May 27, 1947 N INTERNAL-COMBUSTION ENGINE Leonard A. Guaraldi, Somerville, Mass. Application November 1, 1945, Serial No. 625,999

3. Claims.

This invention relates to improvements in internal combustion engines More particularly it relates to two-cycle engines which may be of fractional horse power sizes suitable for driving model airplanes and the like and which, in larger sizes, have general utility for propelling airplanes and vehicles generally, and for supplying motive power wherever a compact, light-weight and eflicient engine may be requisite or desirable.

It is an object of the invention to provide an internal combustion engine whose volumetric elil.-

ciency ratio is increased as compared with comparable prior engines, and whose crank case is maintained free of explosive gases. According to the invention a relatively highly compressed fuel mixture is released into the outer end of the cylinder thereby to provide an increased volume of fuel mixture in each charge as compared with prior procedures. The cylinder has an inner end wall separating the interiors of the cylinder and crank case, and the incoming fuel mixture is com pressed on the inward stroke of the piston and is then by-passed to the outer end of the cylinder. No fuel mixture passes into the crank case, the presence of which in the crank case of prior comparable engines has been a source of great danger, especially in the larger sizes ofengines.

Another object is to provide a two-cycle internal combustion engine whose piston has relatively short axial extent and whose cylinder is correspondingly relatively short with rigid closure walls at its opposite ends, and with a rigid shank on the piston extending slidably through the inner end wall of the cylinder and connected outside of of the piston axially of the piston to the extreme' outer end of the cylinder. It is, moreover, my purpose and object generally to improve the structure and operation of two-cycle internal combustion enginfes.

In the `accompanying drawings:

Figure 1 is a side elevation of a two-cycle internal combustion engine embodying features of my invention f t Figure 2 is a cross-sectional view on line 2-2 of Figure 1; and

(c1. 12s-v4) Figure 3 is a view similar to Figure 2 of a modied form.

Referring to the drawings, a two-cycle internal combustion engine is represented which may be considered representative of two-cycle engines generally whether of fractional horse power capacity or made in any of thelarger sizes suitable for supplying the motive power for airplanes and other vehicles, for example. While a single cylinder engine is shown, obviously the number of cylinders may be multiplied as may be desired and the cylinders in a plural or multi-cylinder engine may be arranged as desired.

In the drawings, the crank case I may be cast with mounting ears I2 projecting at opposite sides, and the ears may have holes I3 therein for reception of bolts or screws for securing the env gine as a unit to any suitableand convenient support. The main body of the crank case, as shown, depends below the plane of ears I2 and the'usual top opening I4, according to the invention, is closed by a plate I6, in'the form of Figs. 1 and 2, or a plate I1, in the form of Fig. 3, which constitutes an inner end wall for the single cylin- 25.der I8 which is iianged as at 20 for securement by screws 22 to the -crank case, with the plate I6 or Il intervening between the flange 20 and the crank case and with the screws extending through the `plate and securing it as well as the cylinder I8 in place. Y

Referring to Figs. 1 and 2, the plate I6 has an axial boss 24 projecting into the cylinder chamber 2B and the boss has an axial hole 28 therethrough within which is mounted a bushing 30. A piston 32 is operable within the cylinder chamber 26 and has an axially depending shank 34 rigid thereon extending with sliding fit through the bushing 30. The piston shank 34 has length such that its inner end projects through plate I6 into the interior of the crank case in all positions of the piston, and the inner end of the shank is pivotally connected to one end of a connecting rod 36 whose other end is pivotally connected to crank pin 38 of crank plate @Il which is secured `preferably engages aroundv the shank 3d at the end of the plate boss 24, it being shown as screwed on the end of the boss.

Piston 32 has short extentl axially in cylinder any suitable source is conducted through supply conduit 4d to the carburetor indicated generally at 6B whence the fuel mixture enters the cylin'der I8 through inlet port 48. on the inner side of the piston, on the latters outward vor comon theend of crank shaft 42. A packing nut d3 I8 and the cylinder is relatively short. Fuel from piston 32.

. operation,

pression stroke. According to the invention, howeverfeach newly admitted charge of fuel in cylinder IB is confined within the cylinder chamber during the major portion of inward movement of piston 32, the plate I6 and packing nut I2 effectively preventing escape into the crank case of any of the newly entered fuel mixture. Hence each new charge becomes relatively highly compressed on the inward stroke, the initial inward movement of the piston closing the inlet 'pcrt, and nal inward movements ofthe piston uncovering the exhaust outlet l and then the outlet port 52 of a by-pass conduit I4 whose inlet port B6 is constantly open at .the inner side of As soon as ythe piston moves inward enough to uncover the by-pass port 52, the relatively highly compressed new charge of fuel on the inner side of piston 32 is released into the outer end of cylinder i8 and the pressure of the charge thus entering causes forcible ejection of any exhaust gases remaining from the previous explosion. This driving out of exhaust gases is. considerably aided by the deector part 58 on the piston which directs the incoming charge toward the outer end of the cylinder alongvthe cylinder wall opposite the wall-in which exhaust outlet 50 is located, whereby the incoming charge gets behind gases exhausting through outlet |50.

As compared with usual engine construction in which the cylinder is open into the crank case, my present engine attains superior eiliciency due to the attainment of a greater compression of each charge of fuel, vthe greater compression, in.

turn, being due to the larger amount of fuel mixture entering the outer end of the cylinder under relatively high pressure. Where the inner end of the cylinder is open into the crank case, as in prior art, relatively little compression of the newly entered charge can be enacted on the ln ward stroke of the piston and the charge. when by-passed to the outer end of the cylinder, is less' effective for driving out spent gases and less fuel mixture gets into the outer end of the cylinder on each cycle, as compared with the present improved engine in which each charge is relatively highly compressed when by-passed to the cuter end of the cylinder.

In the case of plural and multi-cylinder engines, my present' construction and manner of eliminates the need for a separate crank case chamber for each cylinder as required in prior comparable engines. Whereas a crank case chamber, sealed with respect' to adjacent crank -case chambers. has served in eect as a continuation of the associated cylinder in prior v comparable engines, my present invention makes it practicable to have a crank case common to all cylinders with no dividing walls or sealed chambers.

In the embodiment shown in Fig. 3, the by-pass from one side to the other of the piston .is axially through the piston. In this case the cylinder 60 is mounted as in the previous case, with the plate i1 constituting the inner end wall of the cylinder. The rigid depending shank 62 of piston 86, however, is tubular and its axial passage opens through the outer end of the piston.

The shank extends inward through bushing 8B- in the boss 88 of end plate i1 and has its inner end connected at 10 to the connecting rod 12, as in the previously described embodiment.

The outer end wall 14 of cylinder 60 has a rigid depending tubular shank 16 nicely iltting slidably in the tubular shank 52' and terminating short of the plane of the inner end wall i1 of the cyl- 75 shank inder. The inner end of tubular shank 18 is closed as at 18.

The fuel supply to the engine of Fig. 3 may be as in the form oi' Figs. 1 and 2, but the exhaust from cylinder preferably is through an annular series of equally spaced holes 80 in the cylinder walls. With the piston 84 in its position of Fig. 3, and assuming that a fresh charge of fuel has entered the cylinder on the inner side of the piston, the inward stroke of the piston will compress the fresh charge which will be confined within the inner end portion of the cylinder until the piston approaches its inner limit of travel. Nearing its inner limit, the piston first uncovers lthe annular series of exhaust holes 80 at the outer side of the piston, and then holes 82 in piston shank 62 come into register with holes 84 in shank 18 to permit the compressed charge to enter the axial passage of shank 18 and to pass thence into the outer end of the cylinder through holes BB in shank 16, close to the outer end wall 14. Hence, as in the previously described case, the compressed charge is by-passed from the inner to the outer end of cylinder B0. However, in the present modification, the new charge enters the outer end @fthe cylinder at the outer end of the cylinder space and the spent gases exhaust from the cylinder at the inner end of the cylinder space, whereby the entering charge is effectively behind the spent gases forcompletely exhausting them from the cylinder.

It will be obvious that, in both illustrated embodiments of the invention, the rigid piston shank whichis guided axially of the cylinder, eliminates much of the, stress which customarily causes uneven frictional wear between the piston and cylinder walls.

I claim as my invention:

1. In an internal combustion engine, a relatively short cylinder having an end wall at each end thereof, a `relatively short piston operable in the cylinder for relatively high compression of the same charge of fuel both on the inward and the outward strokes of the piston, a rigid tubular shank on the piston extending through the inner end wall of the cylinder. a rigid shank on the outer` end wall of the cylinder extending with sliding fit` axially-within said tubular shank of the piston. means for admitting a fresh charge of fuel into the cylinder on the inner side of the piston during the outward stroke of the piston whereby said fresh charge is relatively highly compressed by the piston on its inward stroke, there being ports in said shanks whereby said compressed charge is by-passed through the Shanks tothe outer end of the cylinder during the final inward movement of the piston.

2. In an internal combustion engine, a relatively short cylinder having an end wall at each end thereof, a .relatively short piston operable relatively high compression of the same charge of fuel both on the inward and the outward strokes cf the piston, a rigid tubular shank on the piston extending through the inner end wall of the cylinder, a rigidshank on the outer end wall of the cylinder extending with sliding fit Yaxially within said tubular shank of the piston, means for` admitting a fresh charge of fuel into the cylinder on the inner side of the piston during the outward stroke ofthe piston whereby said fresh charge is relatively highly compressed by the piston onits inward stroke, `there being ports insaid shanks on the inner iside of the piston and a port in said end-wall close to the outer end wall of the cylinder amines whereby lsaid compressed charge is by-md' to the extreme outer end of the cylinder as the piston approaches its inner limit.

3. In aninternal combustion engine, a relatively short cylinder having an end wall at each end thereof, a relatively short piston. operable in the cylinder for relatively high compression oi the same charge of tuel both on the inward and the outward strokes of the piston, a rigid tubular shank on the piston extending through the inner end wall of the cylinder, a rigid shank on the outer end wall of the cylinder extending with sliding t axially within said tubular shank oi the piston, means for admitting a fresh charge cffuel into the cylinder on the inner side of the piston during the outward stroke of the piston whereby said fresh charge is relatively highly compressed by the piston in its inward stroke, an annular seriesof exhaust ports in the cylinder walls at a location to be uncovered as the piston approaches its inner limit, ports in said shanks on the inner side of the piston adapted to resister when the piston approaches its inner limit, there being a port in said end-wall shank close to the outer end wall oi the cylinder whereby said compressed charge is lay-passed to the extreme outer l end of the cylinder during registration of the shank ports at' the inner side ot the piston. said Aby-passed charge entering the' outer end ot the cylinder behind the spent gases thereinfor effectively driving said spent" gases out through said annular series ot exhaust ports.

LEONARD A. GUARALDI.

REFERENCES crrnn 

